Computer cluster networks constructed with a fat-tree topology are very often used to interconnect the client nodes in massively parallel computer systems. This type of topology is often called a “tree” because of its structure with a trunk, branches, and leafs that ultimately connect to client nodes. In addition, fat-tree networks typically provide communication between client nodes at a constant bandwidth, because the number of connections out of each switch level to the next higher level is the same as the number of connections from the previous lower level. The lowest level includes the “leaves” with ports that connect to the client nodes. High performance computers are being used more and more for essential functions that require higher bandwidth, reliability, and for applications using very large numbers of processors requiring higher availability. To meet these needs, conventional network clusters typically include duplicate fat-tree networks stemming off the client nodes, or dual-rail network configurations. However, the cost of this improved capability is typically double that of a single-rail network.